An Ipswichian foraminiferal assemblage from the Gwent Levels (Severn Estuary, UK)

Abstract

Andrews et al. (1984) documented the occurrence of palaeo-beach deposits underlying Holocene alluvium at Llanwern, inland on the Caldicot (Gwent) Levels near Newport. These deposits at Llanwern (ST360872) lie at −3.6 to −4 m OD and were studied by Andrews et al. (1984) from borehole samples only. The sediments comprised sands and gravels with abundant intertidal and rocky shore molluscs suggesting a beach depositional setting, close to an intertidal lagoon. Locke (1971) also noted the widespread occurrence of coarse basal sands and gravels underlying the Holocene deposits of the Caldicot Levels and interpreted them as an ancient beach. Radiocarbon dates obtained from mollusc specimens yield a date of 25 450 ± 750 BP, indicating a pre-Holocene age. Amino acid racemization (AAR) studies assign these deposits to AAR Group II, oxygen isotope substage 5e, c. 120 000–130 000 BP (Andrews et al., 1984), equivalent to the Ipswichian interglacial of Great Britain.

In the spring of 1991, a coarse yellow sand unit was found exposed low within the intertidal zone (c. −4–6 m OD) on the foreshore at Goldcliff, Gwent (ST374828). The unit occurs stratigraphically lower than the Holocene deposits, which at Goldcliff comprise blue/grey clay and peat of the Wentlooge Formation, deposited under brackish–freshwater conditions (Allen & Rae, 1987). This represents a similar stratigraphic succession to that observed at Llanwern by Andrews et al. (1984) some 4 km inland, and given Locke’s (1971) remarks, the probability is that the coarse yellow sand exposed at Goldcliff is a seaward . . .